88 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



discover the condition. After these cows were removed, 

 the milk from these farms ceased to infect guinea pigs. 

 No clinical cases of udder tuberculosis were found in the 

 other 86 herds examined, but on these farms cows had 

 been sold between the time the milk samples were col- 

 lected and the herd was examined, or the farmer had been 

 buying milk from other sources when the samples were 

 collected. 



Friis inoculated guinea pigs with samples of mixed 

 milk from 28 dairy farms in and about Copenhagen and 

 demonstrated tubercle bacilli in the samples from four 

 farms. On one of these farms two cows with tuberculosis 

 of the udder were found and one cow with udder tuber- 

 culosis was found on another, while on the other two 

 farms cows were found showing physical symptoms of 

 tuberculosis in other organs. There is no doubt that the 

 other twenty- four farms contained cows which would have 

 reacted to the tuberculin test. 



The milk from 12 non-clinical reactors was tested for 

 tubercle bacilli by Klein and Campbell by injection into 

 guinea pigs. These cows were in a stable with 12 other 

 non-clinical reactors which were not included in the ex- 

 periment because they were approaching the end of the 

 lactation period. The stable was light, well- ventilated, of 

 suitable size and clean. The cows were cleaned with a 

 curry-comb and brush and the udders wiped with a damp 

 cloth before each milking. All the cows in the stable were 

 examined by inspection, palpation and auscultation when 

 the experiment began and no symptoms indicating tuber- 

 culosis were found. They were all in a good, thrifty 

 condition and none had a chronic cough. (All suspici- 

 ous animals had been previously removed.) The 12 cows 

 used in the experiment were arranged in groups of three 



